Remove reflection of one object from another object?
Cycles:

Set the renderlayer with the reflective object to Exclude layer one:



Now objects on layer 1 will not have any affect on layer 2.

Example .blend

Blender Internal:

In BI this is more complicated, because it appears to be impossible to separate reflections into separate layers with BI.

In other words, you can either reflect every object in the scene, or reflect nothing (no selective reflecting). You might be able to do something with the Material Index pass, but with even a simple scene it becomes complex quickly.

As a workaround, you can use multiple Scenes.


Create a new scene in the Info panel by pressing the +:



Select one of the options. You probably want Link Objects, but check the wiki for an explanation of each option.
In the new scene, setup a renderlayer that only renders objects on layer 1.
Back in the first scene, setup a renderlayer which has only the reflective object. Put objects you do want to reflect on a different layer, but in the same scene.
Mix the two scenes with an Alpha over node:




Example .blend